Means for controlling air pressure in buildings



S t. 16, 1952 w. w. STUART 2,610,565

MEANS FOR CONTROLLING AIR PRESSURE IN BUILDINGS Filed Dec. 14, 1946 iii/I I INVENTOR.

7 WILLIAM w. STUART ATT'YS Patented Sept. 16, 1952 MEANSTFORIEONTROLLING AIRFPRESSUREE IN BUILDINGSjZ- I WiHiamfW. Stuart, DesMoines; Iowa j H Abliliation'necember' 14, IMGf'SeriaI nastiness? i i 2 Claims: 1

The "purpose of "my inventionis to provide means to maintain; in a" heated "space,such as a house; anairpressure greater than *wouldexi'st;

butrfor-such means.

The maintenance-oi such pressurerwillfmake' 4 combustion conditions of' fires-within the house better; and insure a cleaner-:2, quieter-and a more comfortable house, and will providesome ventil'ation. Also-in some casessome parts'of the equip ment will act "as 'an" indicator in" the variations of the tightnessof the building; This invention will help make possible and feasible the 'construc-' tion' of a house that will costless to build and less to maintain.

Uncontrolled'infiltrationiof air has many detrimental efiects:-- Such infiltration is a result of lower -pressure 'insideithe building than exists outside; Obviously reducing the indoor outdoor pressure difference "byraising"the'iindoor pressure, reduces th-e uncontrolled" infiltration: A chimney exhausts 'air-from ahouse. Infiltrati'ng airbrin'gs dirt into thehousei This infiltration of air-is frequentlyresponsible for annoying drafts: Oftenhouse temperatures "are'i-rnaintainedhigh'erthan"would-otherwise-ice necessary;

in'-order to "offset the chilling eiiect oi" these draits.-- When temperatures are raised; fuel consumption is increased: Thus-air "coming 'into a building'at the wrong place oan'produce'uncom fortable conditions and increase-the cost of heating' the building. Occasionally an opening is-pr'o vided' iusuailyin an outside wallo'f the-'boiler or furnace'room) to admit air to thefire but this air-1s rarely 1 filtered 1 and is often not'suflicienteven for the fire and so'does not stopor even some respects aggravated this'already t ad*ccm'-- bustion' condition. The leaks"where'-'caulking; r

stripping; etc;',:have'not been thorough or well done; are more noticeable than everon-the decorations; *Theseievils are due in part-to dif-" ferencea'between indoor "and outdoor pressures;

In the summeriwith' indoor and-outdoor 'temperatures the i-same' or"nearly the same, and-with doors and windows open; the indoor-outdoor" pressure difierence disappears. The pressure-dir ference appears when the house is "closed and the indoor-outdoor temperature difference increases; As the-heating :seasonadvances; the pressure difference increases and more and more-iair must enteri thehouse because thej'colder the -weather;

theigreaterais the loadonthe heating-plant and 2 the'more air'is-"neede'd for combustion-. This varying need "calls for automatic-controller the amount ofair supplied to theho'use and points to the need of a controlling'meansand method L- such as is described here.

If g the indoorand -'outdoorpressureswere the same,or the indoor= pressurewere above the out door-pressure,there-would*be-nocold drafts due to infiltration: Also the "streaking 'ofwalls and iwoodwork withdirthy infiltratingair would he eliminatedr It has-been observedthat *a'h'ouse l is quieter after-it has been-weather strippedi A reduction in openingsin a'housewillresult ina reduction of street noise-carried' intoa'house;

.lWhfr controlled means of bringing clean air-into a house" is provided, substantial-savings are *ei-' feotedr These" savings" are -'tWo-fold.'-

The'ilrst saving iis" the original 1 cost. "Few windows that open are needed There can be an increased ;use" of 'glass'" blocks and per:

manently set windows, the useof which eliminate such expensive'tvindow trimmings as storm sash, fly screens, handles, locks; z-sash zcordsp'sas-h weights, pulleys, hinges; hangers; slides; weatherstrips and costly windowframessflhe' second saving is in the reduction in maintenance: There is no handling; storing, cleaning,--painting-"and renewing of storm "sash and screens sash cord and'locks, etc. Thissavinggoes on season after season' for the 'useful'flife' of the building" By my present invention Iprovi'de'means'to maintain within. the house aipredetemiined air pressure and to clean the air introduc'edto maintain this pressure, before deliveringit to the" house. My arrangement'makes -it easier to keep 7 out snow, rain, birds,'jmice; insects, etc.

Where pressure is maintained automatically, the position of certain parts, of the pressure equipment can be taken as an indication of the volume of air leaking out of thehouse. A change in the position of these parts. WiIIFindicate a change in the volume of air leaking-out and if the change in said position is not due to wind effector change in .load following the starting or stopping of the heating plant, anexhaustffan or the efiect produced by a-fireplaceor similar cause, it may be taken as indicatin achange; in the.-tightness."of the house; ,In applying the system-to an old leaky house,.it..has been-:found 1 that it'is not practical to carryaninsidepressure.1 as highas the outside; However,- decreasing the indoor-outdoor pressure: difference? improves combustion conditions byreducing-the: tendency. of the firei-to 'be air+s.tarved---: as=when indoor.

pressure is considerablybelow outdoorpressure s;

The size of the equipment and the cost of its operation will depend on a number of factors such as the tightness of the house, the frequency of the opening of doors, and the use of fireplaces and exhaust fans, etc. In a reasonably tight residence the savings in fuel and attention necessary to automatic heating equipment such as soot removal and other heating plant cleaning, seasonal adjustments on burner equipment and in decorations are more than enough to cover the cost of operation of the system.

With these and other objects in view, my invention consists in the construction. arrangement and combination of the various parts of my de-- vice whereby the objects contemplated are attained, as hereinafter more fully set forth,"point-' ed out in my claims and illustrated in the accompanying drawing, wherein the single figure diagrammatically illustrates an embodiment ofmy invention.

The maintenance of indoor pressure involves the supplying of air to the inside of the house. In my invention this air may-be filtered and in the preferred form, the'volume may be varied to meet the varying needs of the house. The air may be moved into the-house by a motor driven blower and at the same time full advantage taken of any wind that tends to drive air into the supply opening. The parts of my invention are so arranged as to prevent the exhausting of large volumes of air from the-house through the air supply inlet opening at those times whenthe Wind is blowing in a direction that tends to produce a suction on the air inlet opening. Increasing the indoor air pressure improves many conditions within the house, such as improving combustion conditions and decreasing infiltration of cold air, dirt and noise. Decreasing infiltration of cold air makes for comfortable conditions especially close to windows where infiltration is normally at maximum. Beyond this there is the added comfort from reduction in drafts and the betterment in healthconditions due to this re- 4 cuits as there shown may be used. If, in place of the control of my patent, a conventional diaphragm control I3 is used with a conventional reversing motor [2 to position the damper H, the air connection to the outdoor side of the diaphragm l8 of the control I3 is made by means of a pipe I4 to an averaging chamber l5. The chamber is connected tothe outdoors on each side of the house by pipes l6, one extending through each of the four walls 2 of the building and terminating with screens l1 outside the walls. The indoor side of the diaphragm l8 of the control -I3 is connected as by a pipe [9, preferably to the space into which the air from the blower duction, the lowertemperature carried and the filtering of the air introduced.

In my preferred arrangement, I provide aduct I passing through the wall 2 of the house, witha weather louver 3 in its'outdoor end through which air is drawn. After passing through the louver the air passes through an air filter 5vto, a chamber C. From the chamber C the air can pass to the house through the opening 6 having acheck valve 1. This check valve swings open whenever the air pressure in chamber C is slightly higher than the pressure on the house side of the check valve 1. Otherwise the check valve stands closed due to gravity acting on a weight 3. The weight 4 is adjustably mounted on thev check valve 1 by means of a stud 4a on which the weight is threaded. V

Another opening 8 in the wall of the chamber C provides for passing air through a pipe 9 from the chamber to theinlet 9a. of a motor driven blower Ill. The blower Hlhas an outlet iU'a discharging within the house and is driven by a motor M which can be started and stopped manually or may be controlled in conjunction with other equipment. 7

Suitably located as inpipe 9 is a control such as a butterfly valve or damper ll. When the indoor pressure is to be controlled automatically, this damper is positioned by a drive mechanism controlled by an indoor-outdoor differential pressure control. This control may take the form of the draft sensitive device of .my Patent No. 2,285,749.; Figure 3, and such drives and such cir- I0 is deliverednormally the furnace or boiler room. The control [3 has contacts l3a and 13b for actuating the reversing motor l2 in a damper closing direction when contact is made at l3a and a damper opening direction when contact is made at [3b.

The blower motor M is arranged in a circuit,

closed according to both indoor-outdoor pressure differences and temperature. To control this circuit I provide a switch 12a on the damper operating shaft of the motor l2 and a thermostatic switch T. The position of the switch [2a is adjustable relative to the motor arm 12b which actuates the damper crank [20 through a link.

12s. The switch |.2a being mounted on the damper motor i2 is actuated by it and can headjusted to stop the blower l0 when the volume control damper has reduced the volume of the air being introduced tothe house to a predetermined low. When the damper ll'is moved'in the direction to increase the volume of air delivered to the house and reaches a predetermined point in its opening movement, the switchv l2a closes the circuit to the motor-driven blower- I0,

setting the blower in operation. In this operation the damper motor [2 is continuouslyin service and controlled by the diaphragm control 13.

The thermostat T is subject to both the temperature of the space into which the blower l0 discharges outside air and to the temperature of the furnace.

0 can operate. The thermostat provides againstfreeze-ups which would result if very cold air were blown into the house at a time Whenthe heating system is-out of order or out of fuels It is therefore set just above freezing, for instance 35 F., so that upon failure of the heatingplant reflected by the absence of heated air from the pipe 2i), the near-freezing outside air discharged at ma will open the-thermostat and thus stop the blower. Aslongas the furnac is functioning the thermostat will stay closed so that under normal conditions, the switch 12a, responding to differential pressure indoors and outdoors, .will' be the controlling factor for the' blower motor M.

tact 22 connected in circuit with a signal light 23 to provide a warning that temperatures are dangerously low due to failure of the heating plant or so low outsidethat the heating plant cannot keep the thermostat :warm enough sci It may be located in respect to the discharge conduit Illa as illustrated and The thermostat 'I' may alsohave a second conthat it closes against the contact 2|. Obviously of course a buzzer or bell may be substituted as an audible element for the signal light 23.

It is possible to use the blower of a forced warm air heating system to draw in outsid air, and there are conditions where this blower could be substituted for the blower I0 of the figure but as it frequentlyhappens that the heating plant blower is not in operation when there is a great need for introducing air from outdoors, this use of the heating plant blower has not been found as satisfactory as the use of a special blower used only for introducing outdoor air.

The use of thefurnace blower for the dual purpose of moving air through the heating system and for introducing outdoor air, complicates the control problem and does not eliminate the need for a separate blower at times when the furnace blower is not in operation. Where hot water and steam heating plants are used, a blower for maintaining the desired indoor-outdoor pressure differential must of necessity be provided.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

I claim as my invention:

1. Means to provide predetermined air pressure in-a building, comprising a duct for admitting air to a building, a blower in said duct, means for starting and stopping the blower according to the difference in pressure inside and outside the building, said means including an averaging chamber connected with outside air on at least two sides of the building below the roof of the building, and a pressure sensitive element subject on one side to pressure within the buildin and on the other side to pressure in the averaging chamber.

2. Means to provide predetermined air pressure in a building comprising a duct for admitting air to the building, a check valve for said duct to admit air to the building when the blower is not in operation and the indoor pressure is below the outdoor pressure, a blower for said duct, a damper in said duct, means for starting and stopping the blower according to the difierence in pressure inside and outside the building, said means including an averaging chamber connected with outside air on at least two sides of the building below the roof thereof, a pressure sensitive element subject on one side to pressure within the building and on the other side to pressure in the averaging chamber, a two-way switch closed one way by said pressure sensitive element when inside pressure exceeds outside pressure and closed the other way when outside pressure exceeds inside pressure, a reversing motor for modulating said damper, said reversing motor being controlled by said two-Way switch, and a switch for said blower opened adjacent the end of the movement of said reversing motor in response to said two-way switch when closed, said one way with said damper near closed position, and closed in all other positions of said reversing motor.

WILLIAM W. STUART.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

